package nc;
import java.util.*;
import org.junit.*;

public class Yuanjing {
    
    static class Main1 {
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            int n = sc.nextInt();
            sc.close();

            int cnt = 0;
            while (n > 0) {
                int t = n / 5;
                cnt += t;
                n = t;
            }
            System.out.println(cnt);
        }
    }

    static class Main {
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            String s = sc.nextLine();
            sc.close();

            char[] cs = s.toCharArray();
            int n = cs.length;
            char[] stack = new char[n];
            int idx = -1;
            // int cnt = 0;

            for (char c: cs) {
                if (c == '[' || c == '{') {
                    stack[++idx] = c;
                } else if (c == '"') {
                    if (idx < 0 || stack[idx] != '"') {
                        stack[++idx] = c;
                    } else {
                        idx--;
                    }
                } else if (c == ']') {
                    if (idx < 0 || stack[idx] != '[') {
                        System.out.println(false);
                        return;
                    }
                    idx--;
                } else if (c == '}') {
                    if (idx < 0 || stack[idx] != '{') {
                        System.out.println(false);
                        return;
                    }
                    idx--;
                }
            }
            System.out.println(idx < 0);
        }
    }

}
